Two-tank wiered reservoir and method of use

ABSTRACT

A method and apparatus for collecting agricultural manure in a confined animal feeding operation includes a separator which receives heavy manure removing particulate from suspension to produce light manure. Heavy manure is collected to a volume of heavy manure sufficient to substantially fill the first tank. Within the first tank, particulate migrates, due to the influence of gravity to form a layer containing manure comprising a lesser density of particulate than is present in the volume of heavy manure. Additional heavy manure buoys the layer such that the upper surface exceeds a height of a weir. The weir is situated in a channel communicating between the first tank and a second tank configured to receive light manure from the separator.

PRIORITY CLAIM

This application claims priority from and entirely incorporates theProvisional Application filed as Ser. No. 61/987,854 on May 2, 2014,entitled “Manure Management Using Centrifuge” by David DeWaard.

FIELD OF THE INVENTION

The present description sets forth a manure and water management systemfor livestock, specifically for managing distinct qualities of liquidmanure.

BACKGROUND OF THE INVENTION

Water use is essential in all dairies. Drinking water is indispensableto sustain life of cattle; some additional water is necessary forcleaning and sanitation procedures; moderate further amounts areimportant in periods of heat stress for evaporative cooling of cows toimprove animal production and health; and additional amounts can be usedin labor-saving methods to move manure and clean barns by flushing inproperly designed facilities. The more water a farm uses, however, thegreater the potential for surface runoff and penetration to the groundwater, with possible environmental impacts offsite. Heightenedenvironmental concerns and the need for resource conservation haveresulted in the implementation of water use permits and other possibleregulatory actions. Thus, it is important to ascertain how much water isnecessary for all the various procedures to operate a dairy and to lookfor ways to reuse some water when to do so is feasible.

To give a very rough scale of manure production, typical dairy animalsproduce about 1.61 ft³ (12.0 gallons) of fresh manure (feces and urine)per 1,000 lb. according to their average live weight per day. Additionalsolids add to that volume and come from wasted feed, horn, tail, andhoof fragments, free stall bedding, and soil tracked in from outsidelots. Additional water is often added to that present in the dairy fromwater wastage, milking center waste water, water used to clean floors,and “flushing” of alleys. When facilities are designed with concretefloors they are generally engineered with enough of a slope to permitthe use of water propelled by gravity to move manure, known as flushing.Flushing is a clean and labor-saving method for moving manure out of thescope of the dairy animal's activities. A flush flume system uses theadditional movement of fast flowing water in gutters to transfer manureacross the width of a barn or across several barns. A high volume pumpcreates an adequate flow rate to prevent settling of manure solids andbedding material within the gutters.

The amount of water used for flushing per cow will vary widely,depending on the size and design of facilities and the frequency offlushing, and because of differences in design, the necessary amount ofwater will need to be individually calculated for each dairy. Generally,usually a “flush” of about 10,000 gallons is needed to clean an alleywidth of 10 to 16 feet. If four alleys are common for every 400 cows,and the alleys are flushed twice daily, this would be an average use of200 gal./cow/day. Many dairies use more than two flushings per day. Butwater is not free, nor is the disposal of waste water. Understandingthese volumes, one can readily appreciate the value of any waterreclamation, by separating water from the manure it entrains in thegutters, as having a great and positive effect on the economics of adairy.

Dairy manure is a complex mixture of two vastly differentmaterials—water and undigested feed. Typical material proportions, forinstance, are such that in 115 lb. of manure at 15% solid content and abulk density of 62 lb./ft³ might be mixed with 55 lb. of sand at 95%solid content, and a bulk density of 110 lb./ft³. When added in theseproportions, the result is 170 lb. of “heavy” manure at approximately40% solid content and a bulk density of about 72 lb./ft³. At theseproportions, sand held in suspension will not settle out of the manurebut can be held largely indefinitely, causing the manure to be highlyabrasive when pumped. For that reason, the more dilute the manure, themore suitable for use in the flush or flume dairy.

Gravity enables the first form of reclamation; the managing dairymansimply stores manure-laden water flowing from the gutters in a receptionpit (a smaller tank for short-term storage to facilitate separation) orin lagoons (larger ponds that operate identically) and allows, overtime, the solids to settle out of the water. Sooner or later, however,reception pits and lagoons become choked with the accumulation ofsolids. The diversity of waste presents its own problems because thegutters contain not merely manure but other solids such as bedding andother unwanted material draw entrained to the lagoon. Wooden hoofblocks, breeding gloves, plastic pieces, rocks and neck straps will clogpumps and create problems in different points in the system. Yet,because organic waste in the manure had value as fertilizer or as aprecursor to fuel, the prudent dairyman would want to recover both ofthe water and the organic solids separate from inorganic waste. To do somakes pure economic sense.

Generally, the settling rate of particles within manure is affected bythe particle's attributes (specifically, the size, shape, and density)relative to the density and viscosity of the liquid being passedthrough. If a particle is sufficiently large and dense, it will settleout of suspension as a discrete particle, such as a rock drops through acolumn of water. As a particle settles, it accelerates until thefrictional drag on its surface equals the weight of the particle in thesuspending fluid. Once friction and gravity are equal, the particletravels downward at a constant velocity, called its terminal velocity.

If there are many particles falling at the same time, the relativevelocity between the particle and the fluid passing over it increases,since the space between particles is smaller. If the space is smaller,and the amount of fluid remains the same, the speed at which the fluidflows must increase. The individual particles slow down as the relativevelocity of fluid acting against them increases. If the concentration isgreat enough, the fluid velocity between particles causes the solids tosettle as a group with uniform concentration. Settling solids appear asa cloud with a distinct boundary between the top of the cloud and theclear liquid above it. The settling of particles as a cloud is calledhindered or zone settling. The speed at which the border between clearliquid and the cloud passes through a column is the settling velocity ofthe slurry.

Merely separating water from the solids is not adequate; the solids inmanure are a nonhomogeneous amalgam which often includes sand as well asan admixture of organic matter and inert solids in diverse sizes. Whensuch solids are suspended in manure, the suspension presents a necessityof sorting the solids in the course of removal. Vegetable matter iscompostable, digestible, and flammable. Plastic gloves, metallic debris,and the like, diminish the utility of this vegetable matter. Naturally,it is easiest to remove these items early on and most advantageously,without requiring manual picking from the manure. Because they are somuch larger in size than the remaining suspensions within the manure,screens prove advantageous for a first removal mechanism, and are oftensituated in the gutters themselves or at the gutter outlet toimmediately remove them from the flow before any of the remainingsmaller particulate matter is addressed.

One inorganic solid that can generally be removed from suitably dilutemanure is sand. Removing sand from manure is advantageous in order topreserve rotating machinery operating in the dairy, particularly pumps.Sand is extremely pernicious relative to the equipment in a dairy. Insome dairies, sand is used as bedding and, thus in these dairies themanure includes large volumes of sand. Additionally, even when sand isnot used for bedding, cows will excrete several pounds per day of gritthat are passed through from the feed they receive. Cows also track sandinto the dairy. Sand is abrasive, and when moving in manure, sandabrades the surfaces it contacts. A manure handling system as taughtherein will include a properly managed sand separation system. Intypical embodiments, the gutter system will include either of a sandlane or a settling pit, or grit chamber, to remove heavy sediment fromthe system before further processing.

Sand separation lanes have come into conventional dairies as effectivein the removal of some sand from manure, and by doing so, thepreservation of manure handling equipment. Separation is based upon thedistinct densities of the matter (i.e. water has a density of 62 lb./ft³whereas sand densities vary between 120 lb./ft³ to 150 lb/ft³). Wherethe flow of the heavy manure is slow enough, and where the suspension issuitably diluted with water, sand will settle out of the manure. Thesettling of sand in separation lanes allows for the periodic removal ofsand from the lane in a manner that is more convenient than dredging alagoon in regular dairy practice. Manure emerging from sand lanes isreadily pumpable and it can often be used to motivate manure in gutters,though, as expressed above, most dairymen would want to reclaim theorganic matter within the manure.

A typical sand separation lane is about 12 feet wide, several hundredfeet long, with a slope of up to ¼% (or 3 inches per 100 feet inlength), and an energy dissipater/flow dispersion system at the inletend. The length of the lane depends on the size of the sand grains; withlonger lengths needed for smaller sand grains. Often made of concrete,sand settling lanes are only a few feet in height, and a typical systemwill have two lanes to allow one to provide for drainage and clean out,while allowing the other lane to be in use. The dairyman can clean outthe lane with a front end loader rather than having to clean the sameout of storage lagoons.

Organic matter is reclaimed by any of screens, presses, or centrifugesto further remove suspended solids from manure. Used together or asdistinct systems, these devices each separate with distincttechnologies. For example, a screen is the most common method, oftentimes poised within a gutter to remove the solids, the most common formis positions obliquely to the flow such that debris within the flowexploits its kinetic energy to be strained from the flow and to ride thescreen up and out of the flow. Other forms exist as well but the mostfrequent exploits, in some manner, the oblique screen in order toprevent clogging.

A dewatering screw press also separates liquids from solids. Such ascrew press can be used in place of a belt press, centrifuge, or filter.It is a simple, slow moving device that accomplishes dewatering bycontinuous gravitational drainage. The most commonly known screw pressof this design is said to have been invented by famous Greekmathematician Archimedes and is known as the screw conveyor. The screwconveyor consists of a shaft, which is surrounded by a spiral steelplate, similar in design and appearance to a corkscrew. Gravity, too,presses water through perforations in the wall. That water is returnedto the dairy while the solids are removed for other use, such ascompost.

The most thorough dewatering device, generally used in conjunction witha screen as a preliminary separator is the centrifuge. For purposes ofthis application, it is useful to refer to two qualities of manure-ladenwater. The first of these shall be referred to as “light manure,” havingapproximately one percent organic solids. The second is somewhat lessdilute, but often usable for flushing is “heavy manure.” The most commonsource of heavy manure is the intermediate water discussed above ascoming off of the sand lane or other sand separation device. Heavymanure comprises from two to five percent organic solids, or, roughlybetween two to five times as much of the organic solids present in lightmanure. Of the two, light manure, carrying a lesser weight of organicsolids, is the more desirable for use as flush water. Nonetheless, wherelight manure is not available, heavy manure, after sand separation whereavailable, can serve as flush water.

Most commonly, a centrifuge is used to separate organic solids fromheavy manure to yield light manure for flushing. A centrifuge is adevice which employs a high rotational speed to separate components ofdifferent densities. The decanter is used for the separation of two ormore phases of different specific gravity; in particular for theclarifying of liquids in which suspended solids are present. Theseparation of solids and liquids takes place within acylindrical/conical rotating bowl, drawing the more dense organic solidsthrough the heavy manure to accumulate on the periphery for removal fromthe resulting light manure.

Decanter centrifuges have a characteristic that dictates selection of anappropriate size. The spinning mass of the centrifuge is its mostnotable feature. Great amounts of energy are expended to bring thecentrifuge up to its operating rotational speed. Frequent run and stop,deceleration with high inertia load, and overhauling torque tend toexpend great amounts of energy and energy has a great cost. Theoptimally sized decanter is one that can exactly process all of themanure produced in a twenty-four hour period in twenty-four hours. Whena centrifuge is idle, it is costly to return it to operation. Inoperation, the most efficient use of the centrifuge requires it to beconsistently and constantly running.

Having described the separation mechanisms that make up a modern dairymanure management system, it is now possible to discuss the problemscommon with uniting them in a single system—optimization. The duty cycleof one means of separation may not correspond exactly either to use orto conveyance of water or manure within the dairy. Production of manureis, by its nature, intermittent. Most farmers milk their cows twice aday, but in a robotic milking system, cows sometimes choose to be milkedfour to five times a day. This doesn't necessarily mean that they areproducing more milk, nor is it uncomfortable for them; calves wouldnaturally feed at four to six hourly intervals. Flushing, then, must becoordinated with the milking times. Production of manure and collectionby flushing varies, then, throughout the day. So, in contrast, by way ofexample, to the centrifuge, production of manure is neither constant norconsistent over a twenty-four hour interval. To achieve the describedefficiency of the centrifuge, there must be some manure held in reserveto feed the centrifuge when the production of manure by the cattle dropsoff.

To address this fact, tanks are routinely used as buffers forintermediate storage of light or heavy manure within the circuits whichthe water and courses within the dairy define. The capacity of suchtanks, however, is itself problematic. To make each tank large enough toact as a buffer for the needs of the “downstream” processes can beexpensive. In a dairy where flushing is not continuous, the tank must besized to contain a twelve- or twenty-four hour capacity, so as to smooththe fluctuations in flow due to the vagaries of use.

As a construction cost, excavation and erection of tanks is one of thegreater expenses in the construction of a modern dairy. Depth is moreexpensive than breadth in construction. In operation, depth is alsoexpensive as the inevitable dredging of accumulate is more expensive asthe depth increases. But volume is a relationship between these twovariables. Additionally, the size of the footprint of any tank is anarea of land that is not otherwise usable on the dairy. Naturally, thelarger the footprint, the greater the capital cost of water reclamation.Economics, being the cruel mistress she is, will dictate that the scarceresources of land ought to be used in the smallest measure, whereverpossible.

What the state of the art does not well provide is a means of reducingthe size of these tanks between processes for handling water within thedairy. The smaller the tanks necessary, the smaller the capitalexpenditure and, thus, the more efficient the dairy. The method andsystem that are described and claimed below provide a more efficientmeans of water management in dairy husbandry.

SUMMARY OF THE INVENTION

A method and apparatus for collecting agricultural manure in a confinedanimal feeding operation includes a separator which receives heavymanure removing particulate from suspension to produce light manure.Heavy manure is collected to a volume of heavy manure sufficient tosubstantially fill the first tank. Within the first tank, particulatemigrates, due to the influence of gravity to form a layer containingmanure comprising a lesser density of particulate than is present in thevolume of heavy manure. Additional heavy manure buoys the layer suchthat the upper surface exceeds a height of a weir. The weir is situatedin a channel communicating between the first tank and a second tankconfigured to receive light manure from the separator.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred and alternative examples of the present invention aredescribed in detail below with reference to the following drawings:

FIG. 1 depicts a flow of heavy manure into a two-tank weired reservoircomprising a communicating channel between the tanks;

FIG. 2 depicts formation of a water layer on heavy manure in the firsttank of a two-tank weired reservoir;

FIG. 3 depicts a flow of heavy manure buoying the water layer on heavymanure in the first tank of a two-tank weired reservoir driving waterover the weir into a second tank;

FIG. 4 depicts a flow of light manure into the second tank of thetwo-tank weired reservoir;

FIG. 5 depicts a flow of light manure into the second tank of thetwo-tank weired reservoir driving a further flow of light manure overthe weir into the first tank;

FIG. 6 depicts a flow of heavy manure buoying the water layer on heavymanure in the first tank of a two-tank weired reservoir driving waterover the downwardly adjusted weir into a second tank;

FIG. 7 depicts a flush dairy exploiting the two-tank wiered reservoirand a centrifuge;

FIG. 7a depicts a detail inset showing an optional chemical retentionsystem;

FIG. 8 depicts a flush dairy exploiting the two-tank wiered reservoirand a sediment tank serving as separator; and

FIG. 9 depicts either of a hog feeding surface or a dairy exploiting thetwo-tank weired reservoir exploiting a centrifuge without a primaryseparator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the invention is depicted in FIG. 1. Atwo-tank weired reservoir 10 is depicted as comprising a first tank 20and a second tank 30 and having a communicating channel controlled bythe presence of a weir 13 and in the preferred embodiment, weir 13 canbe readily adjusted in height to regulate flow between the first andsecond tanks 20, 30. In alternate embodiments, the channel might be apipe or channel, with or without a distinct adjustable weir, the waterflow being regulated by the vertical height of the pep or channelrelative to the surface levels of the manure present in each of thetanks 20, 30. As explained, it is not a necessary function of thisinvention that the weir 13 or any pipe or channel serving as the weir,itself be adjustable in height, though that feature is present in thepreferred embodiment. No more than an aperture between the tanks isnecessary to achieve the purpose of the invention; and, in the mind ofthe inventor, “weir” as used in the claims includes, as well, a platedefining an aperture. Even the plate defining the aperture, as might bepresent in some embodiments, could be adjustable in height relative tofluid levels anticipated in either of the first tank 20 or the secondtank 30. For purposes of this application, the term weir as used in theclaims will include channels and pipes for the conduct of fluid betweenthe first tank 20 and the second tank 30. That liquid may pass betweenthe two tanks 20, 30 based upon the levels of liquid within the tanks20, 30 is minimally necessary to achieve the objects of this invention.

As described below, in the preferred embodiment, the adjustable weir 13allows a dairyman a simple means for regulating the volumetric flow ratewithin the communicating channel comprising the weir 13. Since thegeometry locating the top of the weir 13 is known and all watercommunicating between the first tank 20 and the second tank 30 flowsover the weir 13, adjustment of the height of the weir 13 likewiseadjusts the volume of fluid flowing between the tanks 20, 30.

In the exemplary embodiment portrayed in FIG. 1, the first tank 20 isdefined between the septum 12 and a first tank exterior wall 22 which,itself, defines a first tank inlet 23. Likewise, the second tank 30 isdefined between the septum 12 and a second tank exterior wall 32 which,itself, defines a second tank inlet 33. For purposes of this explanatorydiscussion, the channel is portrayed as an aperture the septum 12defines. The weir 13 is adjustable in height in order to regulate thevolume of water that will pass over the weir 13.

Parenthetically, the inventor notes, in a modern dairy, manure is movedby employing high volume manure pumps selected to create a flow rateadequate to prevent settling of manure solids and bedding material asthe manure is transported. While pumps are not portrayed in these FIGS.1-6, the presence of those pumps is presumed. Because the movement ofpumped manure into and out of a tank is well-known and as such, thepumps are not portrayed as they add nothing to portraying the characterof the conjoined tanks 20, 30. Rather, the first tank inlet 23 and thesecond tank inlet 33 are portrayed as open flumes in order to show,graphically, the flows into and out of the first tank 20 and the secondtank 30 respectively. While such a flume system as illustrated certainlycan be exploited in an embodiment of the invention, the preferredembodiment will include the high volume manure pumps that are moreconventionally used for manure transport. Nonetheless, in order tobetter portray movement of liquid into the respective tanks herein, thefigures show movement of manure into tanks as issuing from pipes abovethe manure levels. The inventor makes this specific disclaimer that theillustrated embodiment is not the preferred embodiment because of thisillustration convention omitting the display of pumps. With theexception, however, of pumps to motivate the flows issuing from thepipes into each of the first and second tanks 20, 30, the preferredembodiment identically embodies each of the remaining features as theyare portrayed in FIGS. 1 through 6.

Heavy manure 25 flows through a first tank inlet 23 the first tankexterior wall 22 defines, shown here as a flow 26 of heavy manure. Theheavy manure flow 26 conveys heavy manure 25 to collect as a volume ofheavy manure 21 within the first tank 20. Such is the designed purposeof the first tank 20, i.e. to receive and hold heavy manure between theseptum 12 and the first tank exterior wall 22. When the heavy manureflow 26 stops, the organic solids within the contained heavy manurebegin to settle due to gravity.

Just as is the practice with the second tank 30, the contents of thefirst tank 20 reside there to be drawn from in order to supply the waterneeds of a flush or flume dairy. In normal operation, the liquid levelswill fluctuate with the operation of the dairy. Depending upon the needsof the dairy, either tank will receive or provide water based upon flushor flume needs in dairy operation. FIGS. 1 and 4, for example, bothdemonstrate the receiving of liquid in the first tank 20 and the secondtank 30 respectively. As explained above, no pump is shown in FIGS. 1through 6 because the explanation of the working of the system is morereadily illustrated without the pumps. Indeed, the preferred embodimentwill use pumps to move manure into and out of the first and the secondtanks 20, 30.

Referring now to FIG. 2, when not agitated, the volume of heavy manure21 in the first tank 20 will tend to settle, producing a film or layerof water 24. Settled particles form a sludge layer at the bottom of acolumn the first tank 20 defines. When the free-falling, settlingparticles reach the top of the sludge layer, they decelerate as thespace between particles becomes smaller, and the velocity of liquidincreases. The pressing of particles together squeezes liquid frombetween them. Concentration of solids increases as the sludge layerdeepens. As depicted in FIG. 2, particles fall from the raw heavy manure21. Settling of particles in the volume of heavy manure 21 causes alayer of water 24 to form. The effect is well-known and is bestexplained from the vantage point of a single particle which floats onthe more dense suspension of particles beneath it. Consider generally,the first of the particles to fall out of the raw heavy manure 25,leaving the region generally where a film of water 24 forms as theparticles leave that region. As gravity draws the particle downwardalong with other like particles that might be present in the raw heavymanure 21 causing the density of particles locally to increase therebyslowing the particle's travel downward. As more particles fall to thelower region of the first tank 20, a film of water forms above aboundary as that boundary becomes better defined. As time passes, thefilm waxes to full layer of water 24 shown herein, spanning anencompassed surface area of the first tank 20. As a short time passes,the density of particles within the water approaches very nearly that oflight manure 31, such as that stored in the second tank 30. This naturalprocess exploits the advantageously formed layer of water 24, especiallyas this layer is formed in the most immediate neighborhood of the weir13.

Referring now to FIG. 3, the first tank 20, is portrayed receiving afurther flow of heavy manure 26, which, given the heavier density of thevolume of heavy manure 21 moves swiftly through the layer of water 24and settles into the lowest region of the first tank 20. As the receivedflow heavy manure 26 fills the lowest region within the first tank 20the denser heavy manure 21 buoys up the layer of water 24 to a heightexceeding the height of the weir 13, an overflowing that weir 13,initiates a flow of water 17 into the second tank 30. The second tank30, analogous to the first tank 20, is defined by the septum 12 and asecond tank exterior wall 32 (within includes a second tank inlet 33that the exterior wall 32 defines).

For purposes of this application, light manure 31 resides in the secondtank 30 and has been clarified by, for example, some of the processesdescribed in text below in reference to FIGS. 7 through 10 below. Thevolume of light manure 31 within the second tank 30 is certainlysuitable for use as flushing water. Likewise, the flow of water 17introduced into the second tank 30 are suitable for use as flushingwater and this introduction of the flow of water 17 into the second tank30 does not compromise the use of contents of the second tank 30 asflushing water.

Referring now to FIGS. 4 and 5, the second tank 30 serves as therepository for light manure 31, as light manure 31 is expelled throughthe second tank inlet 33 which the second tank exterior wall 32 definesto establish a flow 36 of light manure 31. The duty cycles of the dairyseparation machinery causes the volume of light manure 31 to varythroughout a cycle of operation of the dairy. The purpose of the secondtank 30 is to serve as the buffering reservoir for the output ofseparators such as the centrifuge or, by way of a second non-limitingexample, the sand lane, just as the first tank 20 serves as a bufferingreservoir for the input of the same separators.

Again, analogous to movement of water into and out of the first tank 20described above, from time to time, the volume of light manure 31 willexceed the capacity of the second tank 30, generally due to the flow 36of light manure 31 through the inlet 33 the second tank exterior wall 32defines. Naturally, as the density of light manure 31 is, by definition,far less than the density of the heavy manure 21, the introduction oflight manure 31 into the first tank 20 could not have any adverse effectupon any downstream manure handling machinery. In fact, the introductionof the liquid to the heavy manure 21 is likely to accelerate thesettling of sand to form the layer of water 24 depicted herein. In manycases, the introduction of light manure 31 in a flow 16 (as shown inFIG. 5) will reduce the viscosity of the heavy manure 21 by dilution,thereby allowing particles from the water layer 24 to settle morerapidly. Thus, when operations cause an excess of light manure 31 toaccumulate in the second tank 30, the flow 16 from the second tank 30 tothe first tank 20 does not adversely affect operation of the dairy.

As asserted, the presently preferred embodiment as depicted in FIG. 6,the dairyman has adjusted the height of weir 13 to be lower in height,thereby reducing the volume of each of the first tank 20 and the secondtank 30 might receive, before any flow 16 or 17 between the tanks 20, 30might occur. Such a feature might be used, either for tuning the manurehandling system as a whole or to adjust to variations in volume ofmanure either light manure 31 or heavy manure 21 within the system.Thus, in the preferred embodiments of the invention, the height of theweir 13 is adjustable to allow the dairyman to adjust that height as the“fine tuning” used advantageously to promote efficient operation of thedairy. Naturally, the volume of the manure handling system can also becontrolled by other means as well, for example, by sending excess liquidto long term storage in a lagoon. It will be readily recognized bypersons skilled in the art that an adjustable weir 13 allows thedairyman to optimize timing and volumes of the flow 17 between the firsttank 20 to the second tank 30 and the flow 16 from the second tank 30 tothe first tank 20. Naturally, when a dairyman extends the weir 13upward, the dairyman increases the volume of each of the first tank 20and the second tank 30 before a flow 16, 17 could be instituted betweenthe first tank 20 and the second tank 30. In doing so, the dairyman hasincreased the capacity of the dairy, as in some instances, to addressthe presence of additional cows within the herd. Should the cows be soldout of the herd, the weir 13 is adjusted back downward again to optimizethe volume held within the two tanks 20, 30, relative to the size of theherd and such other factors as the astute dairyman might consider inadjusting the weir 13.

By way of overview, the installation of the inventive reservoir 10 has asignificant beneficial effect upon the design of a modern dairy 1, suchas the design depicted in a process diagram such as in FIG. 7 and adetail of an optional embodiment additionally depicted in FIG. 7 a.

The specific design volume of the two-tank weired reservoir 10 will bedictated by the population and breed of the cattle. Cows differconsiderably in the amount of manure they produce. Jerseys, for example,produce only 60% as much manure as Holsteins. Because of the distinctvariables entailed, no systematic method is published here to calculatean exact relation between volume of manure produced and the combinationof breed and population.

A number of different manure handling configurations are commonly usedin dairy design. A flush system will fill the gutters with motivatingflush water with organic solids entrained in the flush water which inthe course of movement will substantially dilute the solid content ofthe manure. Flushing dairy facilities, such as milking parlors, holdingareas and free stall alleys, can replace mechanical scraping or scrapingwith a tractor and blade. For optimum performance, flushed surfaces areusually sloped at 2 percent to 5 percent to provide adequate flowvelocity for good cleaning and transport. Flush dairies are currently apreferred embodiment of the instant invention as it enjoys certaininherent advantages in operation:

Labor may be reduced.

Flushing systems may be easily automated.

Frequent flushing may result in cleaner facilities and less odor.

Operating costs are lower.

Flushing is suited to a low-labor system incorporating a lagoon andirrigation for storage/treatment and distribution of waste.

Flushing better accommodates large facilities and cow numbers.

Floors dry out better because wet, residual manure is removed.

In a flume system, movement of manure once in conduits is very similarin operation, but requires mechanical movement of the manure into theconduits referred to as “flumes,” rather than to simply rely uponmovement of flush water over the floor surface of the dairy 1. Once theyreceive manure, it is the flumes rather than the floor surfaces that areflushed with flush water to move the manure out of the barn. A flumesystem utilizes fast flowing liquid to transfer manure across the widthof a barn or across several barns, generally in a round tube. A highvolume pumps creates an adequate flow rate to prevent settling of manuresolids and bedding material. Water addition, and separation ordewatering is needed before evacuating to further processing to retainenough liquid to keep the flush flume operating.

From the dairy 1, manure is conveyed by being entrained in the water,through a channel 41 ultimately to the first tank 20, typically agravity pipe, i.e. a pipe placed with sufficient slope to motivatemanure by gravity through the channel 41. In the embodiment of theinvention here depicted, an optional sand lane 5 is used to initiallyseparate sand from the manure. The sand lane 5 is effectively utilizedon both flush and flush flume systems. In a typical sand lane, flush orflush flume water containing heavy manure 26 is introduced into ashallow, long and narrow channel (lane) at a high delivery rate. Anenergy dissipation system is usually installed at the head end of thelane to slow the velocity of the water and distribute the flow over thewidth of the sand lane 5. The bottom of the 12-foot-wide lanesconventionally will be sloped 0.2 to 0.25 percent. The water velocityslows to 1 to 2 feet per second in the sand lane 5 which allows the sandto settle out while washing most of the organic matter from the sand tocontinue through the sand lane 5 into a reception pit 7 by means of achannel 42.

The reception pit 7 sits at the lowest end of the channel 42 to collectmanure from the dairy 1. The reception pit 7 in this exemplaryembodiment is a fabricated manure storage tank of either concrete orcoated metal with a glass lining and may be situated either above orbelow ground, though these are situated in this embodiment to simplyallow gravity to motivate manure through the channel 42. By using theagitator in reception pits the manure is stirred into a homogenous mix,which allows it to be easily transported, by pumping, to the furtherinto the system. Depending on the size of the storage, the agitator maybe used daily or as often as necessary, to maintain the state of themanure.

In the presently preferred embodiment shown, a feed pump 75 transfersthe manure to further separation through a pipe 43 to a primary sandseparator 8. Sand separation may be through any conventional means, forexample, by slope separator, a screen such as a wedge-wire screen, or arotary separator. Naturally, the purpose is to remove as much of thesand as possible by the most economic means. Sand removed, for example,by wedge-wire screening need not later to be removed by centrifuge and,thus, preliminary removal has great and positive impact on the economicsof manure handling. While not specifically necessary for successfuloperation of the two-tank weired reservoir 10, in a presently preferredembodiment, this screening is extremely advantageous and its use occursat the primary separator 8. Sand so removed is generally stacked assolid 2 and in some dairy operations rinsed for use as bedding forcattle. Advantageously, such sand can readily be recovered, used, andreused and where well-tolerated by the cows, it is can be usedeconomically with far greater utility than straw or other organicbedding.

Screen separators 8 include stationary inclined, vibrating, rotating,and in-channel flighted conveyor screens. All separators of this typeinvolve a screen of a specified pore size that allows only solidparticles smaller in size than the openings to pass through. This typeof separator generally works best with manure having a solids content ofless than 5%. In use of a stationary inclined screen, liquid manure ispumped to the top edge of the inclined screen. Liquids pass through thescreen while the solids accumulate on the screen and eventually movedownward due to gravity forces and fluid pressure.

In use of a vibrating screen, liquid manure is pumped onto the flatvibrating screen at a controlled rate. The liquid flushes through thescreen while the rapid reciprocating motion employed moves the solids tothe screen edge where they are collected. The vibration reduces cloggingof the screen. Obviously, the power requirement is higher with avibrating screen system than with the stationary inclined screen.

A continuously turning or rotating screen receives liquid manure at acontrolled rate. The liquid passing through the screen is collected in atank while the retained solids are scraped from the surface into acollection area. A refinement of the continuously turning or rotatingscreen is the In-channel flighted conveyor screen. This screen separatorsystem consists of an inclined screen and a series of horizontal bars,called flighted conveyors. The separator can be placed directly in anopen manure channel, which eliminates the need for a sump or a pit and alift pump. Liquid passes through the screen and drains into the channelon the downstream side of the separator, while the separated solids aredeposited on a collection pad. Uses are similar to those of thestationary inclined screen separators, but the in-channel flightedconveyor screen separator requires more mechanical maintenance, as itsmoving parts are exposed to corrosive and abrasive materials, such assands and chemical constituents of manure.

Presses act as continuously-fed dewatering devices that involve theapplication of mechanical pressure to provide additional separation ofthe manure slurry. They are often used to remove additional water fromthe separated solids portion produced following screening orcentrifugation. This physical separation process typically achieves ahigh level of dewatering and the pressed solid cake can be composted orused for refeeding. The three main types of mechanical filtrationdevices are roller, belt, and screw presses. A fourth type is the filterpress. The more prevalent is the roller press, having two concavescreens and a series of brushes or rollers. The manure slurry isinitially deposited onto the first screen and then moved across the twoscreens with brushes and squeezed by the rollers. The liquids aresqueezed through the holes while the solids remain on the screen. Thefollowing two separators use these principles in their operation. Afurther refinement is the two-stage double roller compression separator.Liquid slurry is force-fed into the first set of perforated separatorrollers. Separated liquid is removed at this point for storage.Separated solids from the first stage are conveyed to the second set ofseparator rollers where the fiber solids are removed by a mechanicalconveyor to the storage area. The liquid fraction is drained off at thispoint and returned to the initial liquid slurry tank. Any of the severalof these might advantageously be used for primary separation 8.

Having separated the major portion of sand from the manure at primaryseparation 8, the sand-separated or heavy manure 21 travels through aconduit such as a channel or pipe to the second tank 30 which functionsas described above with reference to FIGS. 1-6, The weir 13 and septum12 defining the weir 13 are both present as is the second tank 30. Notshown in the previously depicted embodiments is the level sensor 18, inthis case present in the second tank 30. The level sensor 18 serves thedairyman by giving and recording the levels in the tank (or where twoare used, one level sensor 18 assigned to each tank), and allows forpredictions to readily be made as to the optimal positioning of the weir13 in embodiments having an adjustable weir 13.

From the first tank 20, a pump 25 that might also, at times be used foragitation, motivates a stream of manure from the first tank 20 through aconduit 26 where, in this embodiment, a flow meter 29 to an automaticvalve 4 r that in some embodiments are used to admit manure into a pipe47 to feed the centrifuge 9. As is shown, in some embodiments, chemicaladditives might be used to accelerate the aggregation of particulate inthe manure making it easier to remove.

In operation, the automatic valve 4 r would close and both of the intakevalve 4 i, and the return valve 4 b open to admit manure to an optionalchemical separation plant 50. In the presently preferred embodiment, asshown in FIG. 7a a circuit includes two sets of valves, an intake valve4 i and a return valve 4 b to the conduit 57 to feed the centrifuge, anda retention valve 4 r which obstructs manure from bypassing the chemicalplant 50 when closed.

In the preferred embodiment the normally-closed intake valve 4 i andnormally-closed return valve 4 b, both open and the normally openrerouting valve 4 r closes to add the circuit the chemical plant 50comprises to the path of manure through the conduit 26 to the conduit 57to feed the centrifuge 9. Each valve 4 i, 4 b, 4 r will change its stateto the opposite state while at same time making the normally preferredembodiment to comprise a manifold with a single impulse that changes thestate of each of the three valves 4 i, 4 b, 4 r.

Separation of a liquid fraction from the solid fraction of manure can bemade more effective through addition of chemicals to coalesce particlesof organic matter in a solid fraction. In this optional process,chemicals selected to improve the retention of the plant nutrients inthe solid fraction are added prior to mechanical separation in theoptional chemical plant 50. Additions of such chemicals assist with theproduction of a liquid fraction with a composition that is more readilyseparated from the solids and diminishes the energy necessary to performthe separation. Flocculation, coagulation, and precipitation are methodsto enhance mechanical liquid/solid separation. In most suspensions,colloidal particles do not aggregate spontaneously because suchparticles are negatively charged and repel each other. However,aggregation is facilitated by adding either multivalent cations thatcause coagulation or polymers that promote flocculation. The addition ofmultivalent cations also triggers precipitation.

The chemical plant 50 as depicted in FIG. 7a , draws manure through aconduit 56 where chemicals from a chemical tank 53 are introduced into aflow of manure through a conduit 54. The mixed manure chemical cocktailthen proceeds through the conduit 52 and at a retention tank 51 thechemicals are allowed to diffuse through the mix. Naturally, to theextent manure precipitates out, it can be collected from the retentiontank 51. When appropriate in the operation of the dairy, the retainedmanure is drawn out of the retention tank 51 by a retention tank pump 55though both of a conduit 58 and the return valve 4 b to be fed throughthe conduit 57, to the centrifuge 9.

The centrifuge 9 is a device, which employs a high rotational speed toseparate components of different densities. Typically centrifuges 9consist of a horizontal or vertical cylinder which is continuouslyturned at high velocities. Centrifugal forces separate the liquid andsolids onto the inside wall of the cylinder into two layers. An auger,which turns slightly faster than the cylinder, moves the solids to theconic part of the unit where they are discharged. The two types ofcentrifuge 9 separators are centrisieves and decanters. Centrisievesconsist of an inclined revolving drum that is lined with a filter cloth.The slurry to be separated is pumped into the drum center. The liquidleaves the drum through the filter cloth and the solids move bycentrifugal force to the edge of the drum where they are removedseparately.

In the case of decanter centrifuges, an auger, turning at a slightlyhigher speed than the cylinder in which it is contained, moves theslurry to the conic part, where it is discharged. Centrifuges are veryeffective at solids separation and can achieve relatively low moisturelevels. The initial cost is high, however, and the energy requirement isalso quite high in comparison to other systems. The decanter centrifuge,however, is considered as the workhorse of a wide range of liquid/solidseparation activities. Its application to the dewatering of wastesledges has made it a most valuable tool in animal husbandry. Thedewatered solids 2 are conveyed from the centrifuge 9 and can be usedfor example, as compost or to be digested to produce methane.

The effluent is largely pure water and traverses to the second tank 30as sand-separated light manure 31. It is important to understand thatwhile it is not potable, the light manure 31 is almost entirelyconsisting of water 24. As such, it contains very few organic orinorganic solids and is very suitable for use as flush water to beginthe whole cycle again. The second tank 30 is used just for such storage,and to the extent that water 24 from the first tank 20 spills in a flow17 into the second tank 30, the presence of that water 24 will notcontaminate the light manure 31 to prevent its use as flush wateravailable through the flush water pipe 45 at the dairy.

Where too much water is recovered from the manure at the centrifuge 9,two further automatic valves 4 s, 4 t work in tandem to divert the flowfrom the second tank 30 to long-term storage in a lagoon 3. Indeed,nothing prevents use of a ball valve to simply divert manure from thesand-separated manure conduit 35 to flow down the lagoon conduit 49 forlong-term storage in the lagoon 3.

The two-tank weired reservoir 10 is not limited to embodiments wherein acentrifuge 9 is employed. By way of non-limiting example, FIG. 8 depictsa flush dairy 1 which drains manure through a channel 41 into a sandlane 5 where sand is separated from the manure in a first separation toflow into the first tank 20 of the reservoir 10. A feed pump 26transfers the manure to a separator 9. As discussed above, separationmay be through any conventional means, for example, by slope, a screensuch as a wedge-wire screen, or a rotary separator. Naturally, thepurpose is to remove as much of the sand as possible by the mosteconomic means. Solids such as sand are removed by conveyor 19 or bysuch means as a skid loader to where the solids are stacked as solids 2,for such use as is economical.

Sedimentation tank 7 is another form of separator also called settlingtank or clarifier. A sedimentation tank allows suspended particles tosettle out of water or wastewater as it flows slowly through the tank,thereby providing some degree of purification. A layer of accumulatedsolids, called sludge, forms at the bottom of the tank and isperiodically removed.

Manure leaving the separator 9 s travels by pipe 46, in this embodiment,as effluent to such a sediment tank 7 for further settling of solids. Atthe sediment tank 7, light manure can be sent back to the second tank 30through a feed line 35 to fill the second tank 30. Excess light manureis suitable for flushing in its state leaving the sediment tank 7through either a pump 75 into a pipe 41 s to serve as a dedicated flushfor the sand lane 5 or into the second tank 30 as a reservoir for flushwater 31 to supply, through the flush pump 36 f that feeds flush waterthrough a pipe 45 to flush the flush dairy 1. Where an excess of flushwater is present in the second tank 30, the contents of the sedimenttank 7 are shunted by pipe 49 s into the lagoon 3 for long-term storage,thereby being available to “top up” the system by conveyance through thefeed pump 65 through a pipe 49 r to the second tank 30 when necessary.Also shown is the flush flume 45 f should the dairy 1 be configured as aflume dairy rather than a flush dairy. That the two-tank wieredreservoir 10 is so readily adaptable to various configurations givestestimony to its versatility and utility in various manure managementsystems.

Hogs, generally, do not use or need either of sand or straw beddingwhich obviates the need for extensive trapping and separating of sandfrom manure. Such is not to say that there are not some particles ofsand to be contended with but where a decanter centrifuge 9 is in use,systems can be designed without distinct separation means to protect thecentrifuge from the undue wear that sand imparts on moving parts. Thissimplest embodiment of an operating manure management system in a flushdairy or swine farm with flushable sties is illustrated in FIG. 9.

While sharing many of the basic elements of the other demonstratedembodiments illustrated above, the manure management system shown isamong the simplest embodiments of the invention. Still relying, as itdoes, on the two-tank weired reservoir 10, the flush return line 25feeds the first tank 20 as it does either directly or indirectly aftersand separation, as in a lane 5, in every embodiment.

Because there is present, relatively little inorganic solid in themanure 21 held in the first tank 20, the centrifuge 9 is fed at a nearlyconstant rate through the feed pump 26. Drawing from the first tank 20and feeding the centrifuge 9 through the feed pipe 47, the centrifuge 9delivers separated solids for compost. A conveyor 19 delivers these to apad for stacking solids 2.

When the solids have been removed from suspension at the centrifuge 9,the remaining liquid is flush-quality water pumped either to the lagoon3 (not shown) through a lagoon conduit 49 for long-term storage, or, tomeet the more immediate needs of the dairy or swine farm 1 into thesecond tank 30 through a feed pipe 35 for storage as sand-separatedmanure 31.

When needed, the sand-separated manure 31 is drawn from the second tank30 with a flush pump 36 and through either a flush manifold 45 or aflush flume pipe 45 f to clean and entrain manure from the dairy orswine farm 1. And so the process continues exploiting the two-tankwiered reservoir 10 as a principal buffer in the management of manure.

While the preferred embodiment of the invention has been illustrated anddescribed, as noted above, many changes can be made without departingfrom the spirit and scope of the invention. Accordingly, the scope ofthe invention is not limited by the disclosure of the preferredembodiment. Instead, the invention should be determined entirely byreference to the claims that follow.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A method for collectingagricultural manure in a confined animal feeding operation, the feedingoperation having a separator which receives heavy manure removingparticulate from suspension to produce light manure, comprising:collecting in a first tank a volume of heavy manure sufficient tosubstantially fill the first tank; allowing particulate to migrate dueto the influence of gravity from proximity to an upper surface of thevolume of heavy manure thereby to form a layer containing manurecomprising a lesser density of particulate than is present in the volumeof heavy manure; receiving an additional volume of heavy manure so as tobuoy the layer containing manure such that the upper surface exceeds aheight of a weir, the weir being situated between a channel and a wallof which the first tank defines, the channel communicating between thefirst tank and a second tank; and receiving in the second tank, a volumeof the manure comprising the lesser density of particulate.
 2. Themethod of claim 1, wherein the method further comprises: receiving inthe second tank, a volume of light manure sufficient to substantiallyfill the second tank to the height of the weir; and receiving in thesecond tank, an additional volume of light manure, the volume sufficientto overflow the weir and, thereby to flow into the first tank.
 3. Themethod of claim 1, wherein the method further comprises: drawing heavymanure from the first tank to feed the separator; removing, at theseparator, a mass of particulate from the heavy manure to produce lightmanure; and conducting, from the separator, the produced light manure toflow into the first tank.
 4. The method of claim 1, further comprising:adulterating heavy manure to feed the separator with a chemical selectedto increase the mass of particulate the separator removes from a unitvolume of heavy manure to produce light manure.
 5. The method of claim1, wherein the separator is selected from a group consisting of areception pit, a sediment tank, a sand lane, a centrifuge, a slopeseparator, a screen separator, a screw press, a roller press, a beltpress, a filter press, a flighted conveyer screen, and a wedge wirescreen.
 6. The method of claim 1, further comprising; adjusting byeither of raising or lowering the height of the weir to simultaneouslyadjust a first tank capacity and a second tank capacity such thatraising the height of the weir increases each of the first tank capacityand the second tank capacity and lowering the height of the weirdecreases each of the first tank capacity and the second tank capacity.7. The method of claim 1 further comprising: transporting the volume oflight manure to or from a lagoon for long-term storage in order toretain in the second tank a selected volume of light manure necessary toflush manure from surfaces the confined animal feeding operationcomprises.
 8. An apparatus for buffering a flow of heavy manure to aseparator and receiving a flow of light manure the separator produces,the apparatus comprising: a first tank for receiving the flow of heavymanure to retain a volume of heavy manure; a second tank for receivingthe flow of light manure to retain a volume of light manure; a channeldefined by each of a wall the first tank comprises and a wall the secondtank comprises; and a weir situated within the channel to regulate flowalong the channel between the first tank and the second tank.
 9. Theapparatus of claim 8, wherein a weir height is adjustable such that byeither of raising or lowering the height of the weir that raising orlowering simultaneously adjusts a first tank capacity and a second tankcapacity such that raising the height of the weir increases each of thefirst tank capacity and the second tank capacity and lowering the heightof the weir decreases each of the first tank capacity and the secondtank capacity.
 10. The apparatus of claim 8, wherein the second tankdefines a lagoon conduit such that the volume of light manure can beeither removed to the lagoon from the second tank or transported to thesecond tank from the lagoon in order to maintain a select volume oflight manure in the second tank.
 11. The apparatus of claim 8, whereinthe separator is selected from a group consisting of a reception pit, asediment tank, a sand lane, a centrifuge, a slope separator, a screenseparator, a screw press, a roller press, a belt press, a filter press,a flighted conveyer screen, and a wedge wire screen.
 12. The apparatusof claim 8, wherein the first tank defines a separator channel, theseparator channel including a chemical feed configured for adulteratingheavy manure drawn from the first tank to feed the separator, thechemical feed charged with a chemical selected to increase a mass ofparticulate the separator removes from a unit volume of heavy manure toproduce light manure.
 13. The apparatus of claim 8, wherein the firsttank includes a first tank pump to feed the separator.
 14. The apparatusof claim 8, wherein the second tank includes a second tank pump totransport light manure to flush surfaces of a confined animal feedingoperation.
 15. A confined animal feeding operation comprising: a floorsurface defining floor channels for receiving urine and feces fromanimals; nozzles situated to introduce a flow of light manure to thefloor surface to flush urine and feces from the floor surface,entraining the urine and feces in light manure to produce heavy manure;a first tank for reception of heavy manure from the floor channels andcollection of the heavy manure therein; a second tank for storage of thelight manure, the second tank including a pump to feed the nozzles withthe flow of light manure; a communicating channel extending from thefirst tank to the second tank and defining a weir having a weir height;and a separator to draw manure for separation from the first tank and inoperation removing particulate from the heavy manure to produce lightmanure conducted to the second tank.
 16. The confined animal feedingoperation of claim 15, wherein the separator is selected from a groupconsisting of a reception pit, a sediment tank, a sand lane, acentrifuge, a slope separator, a screen separator, a screw press, aroller press, a belt press, a filter press, a flighted conveyer screen,and a wedge wire screen.
 17. The confined animal feeding operation ofclaim 15, wherein the first tank defines a separator channel, theseparator channel including a chemical feed configured for adulteratingheavy manure drawn from the first tank to feed the separator, thechemical feed charged with a chemical selected to increase the mass ofparticulate the separator removes from a unit volume of heavy manure toproduce light manure.
 18. The confined animal feeding operation of claim15, wherein the second tank defines a lagoon conduit such that a volumeof light manure can be either removed to the lagoon from the second tankor transported to the second tank from the lagoon in order to maintainthe selected volume of light manure in the second tank.
 19. The confinedanimal feeding operation of claim 15, wherein the weir height isadjustable such that by either of raising or lowering the height of theweir that raising or lowering simultaneously adjusts a first tankcapacity and a second tank capacity such that raising the height of theweir increases each of the first tank capacity and the second tankcapacity and lowering the height of the weir decreases each of the firsttank capacity and the second tank capacity.
 20. The confined animalfeeding application of claim 15, wherein the first tank includes a firsttank pump to feed the separator.